program fact;
var f,g:text;
        p:longint;



procedure iofile;
begin
        assign(f,'fact.in');
        reset(f);
        assign(g,'fact.out');
        rewrite(g);
        readln(f,p);
        if p=0 then
                begin
                        writeln(g,'1');
                        close(g);
                        halt;
                end;
        close(f);
end;



procedure prel;
var x,diviz,i:longint;
begin
        x:=1;
        diviz:=1;
        while x<=p do
                begin
                        diviz:=diviz*5;
                        x:=x*5+1;
                end;
        x:=(x-1)div 5;
        diviz:=diviz div 5;
        i:=0;
        while p>0 do
                begin
                        i:=i+(p div x)*diviz;
                        p:=p mod x;
                        x:=(x-1)div 5;
                        diviz:=diviz div 5;
                end;
        writeln(g,i*5);
        close(g);
end;




begin
        iofile;
        prel;
end.